1. Field of the Invention
This invention relates to an expanded grid body mainly used with a large-sized lead-acid battery and a manufacturing method of an electrode plate using the expanded grid body.
2. Description of the Related Art
As a manufacturing method of pasted-type lead-acid battery electrode plate, for example, there is the following manner as shown in FIG. 1. That is, a lead or lead alloy sheet 1 is expanded like mesh by an expanding machine 2. A current collector lug part (simply referred lug part) 8 is formed in a non-expansion portion 4. A grid body which is an expansion portion 3 is filled with an active material paste. Thereafter, the grid body is cut by a cutter 9 to separate electrode plates of a predetermined size. This method is high in productivity and so-called expanded electrode plates manufactured by the method are uniform and the mass of the grid body relative to the active material can be decreased, so that weight reduction is possible.
Hereinafter, the width and the height of the grid body or electrode plate will refer to directions when the grid body or electrode plate is placed with the lug part upside.
An electrode plate of a large-capacity lead-acid battery used as a backup power source of telecommunication, etc., or an emergency power source is sized about 150 mm in the width direction, but about 250 to 500 mm in the height direction with a non-expansion portion left as shown in FIG. 2, the expanded portion grows and thus the following disadvantages are included:
Since the height of the expanded portion becomes large, the manufacturing devices are upsized;
handling at the assembling time becomes difficult to perform (warpage, deformation of electrode plate because of insufficient strength); and
voltage drop in the expansion portion becomes remarkably large and poor discharge performance results.
As a method of overcoming these disadvantages, a method of increasing a non-expansion portion 4 in the upper part of a grid body and providing an opening 13 in the increased part (JP-U-58-133271) as shown in FIG. 3, and a method of leaving a non-expansion portion 4 both in margins and in the center and providing an opening 13 in the center (JP-A-2-267864, FIG. 4) have been proposed. However, improvement in the discharge performance is insufficient for a large-sized electrode plate of which is large in the height direction as compared with the width direction. Then, several expanded electrode plates (grid bodies), each expanded in the grid body width direction with a non-expansion portion left in the grid body height direction were proposed in the past (for example, JP-A-54-177525, JP-B-59-51107, JP-B-61-8540, and JP Patent No. 2765020).
Since an electric current flowing into an electrode plate also becomes large in a large battery, it is necessary to widen the lug part width to some extent. However, if the lug part and the non-expansion portion following the lug part are set to the same width, the grid body mass is increased and the active material holding (filling) amount is decreased. Then, in the expanded electrode plates which are expanded in the grid body width direction, the width of the non-expansion portion 4 following a lug part 11 is made narrower than the width of the lug part 11 as shown in FIG. 5. However, the lug part 11 of the grid body of this shape extends off an active material fill part 12 to one side. Thus, as shown in FIG. 6, if an electrode plate using the grid body of this shape is superimposed on an electrode plate different in polarity to manufacture a battery, a portion 14 not overlapping the adjacent electrode plate occurs and the efficiency of active material availability decreases, leading to capacity shortage of the battery. Particularly, in a valve regulated sealed lead-acid battery using a fine glass fiber separator, it is known that a battery with a compression degree of the electrode plate and the separator is inferior in life performance, and there is a possibility that capacity lowering at an early stage will occur because of shortage of the pressure degree in the portion not overlapping the adjacent electrode plate. On the other hand, as shown in FIG. 7, if the electrode plates are placed one upon another so as to completely superpose the active material fill portion 12, current collector lug parts 11 project to a side, thus a battery container 15 must be designated large, resulting in lowering of the volume energy density. Further, a grid body extends in a gap 16 between the electrode plate and the battery container 15, whereby adhesion properties of the grid members with active material worsen, leading to lowering of the battery capacity.
To furthermore improve current collection performance and decrease scrap loss, a mesh part is provided on both sides of a non-expansion portion in JP-B-61-8545. However, if a decrease in the scrap loss is given a high priority, an increase in the grid body mass and battery capacity shortage caused by decrease of the active material filling amount introduce a problem.
To provide an active material mass in the expanded grid body expanded in the grid body width direction, an active material may also be filled into a non-expansion portion. As shown in FIG. 1, to fill an active material into the expanded grid body of the conventional shape, the active material is prevented from being deposited on current collection lug parts 8, because welding becomes extremely difficult to perform if an active material is deposited on electrode plate lug parts when the electrode plate of the same polarity lug parts are welded at the battery assembling process. However, as shown in FIG. 8, in the expanded electrode plate expanded in the grid body width direction, to consecutively fill an active material also into non-expansion portion 4 in a concatenation state of grid body like a belt, the active material is also deposited on the lug parts because the electrode plate lug parts 8 are positioned on the same line as the fill part with respect to the grid body travel direction. To circumvent this problem, it is also possible that the direction is changed after cut to separate grid body forms and that the grid body is passed through a pasting machine with the grid body set perpendicular to the travel direction, but uniformity of filling and the productivity of electrode plates are degraded.
In fact, the expanded grid bodies expanded in the width direction are scarcely used because of the problems.
It is therefore an object of the invention to provide a grid body form that can be intended for reducing the weight of an electrode plate and enhancing the productivity of the electrode plate and a manufacturing method of an electrode plate using the grid body form without degrading battery performance to apply an expanded electrode plate to a large-sized lead-acid battery.
According to the present invention, a lead-acid battery electrode plate manufactured by a process comprises the steps of: (1) consecutively supplying a lead or lead alloy sheet; (2) leaving a part in the vicinity of the center of the sheet as a non-expansion portion and expanding both sides like mesh to form a grid body; (3) filling active material paste into the grid body; and (4) cutting the grid body to predetermined dimensions; wherein the non-expansion portion forms a current collector part of the electrode plate along an expansion portion in an up and down direction of the electrode plate; one or more openings are made in a part of the non-expansion portion; a part of the non-expansion portion is projected above the position of an upper margin of the cut expansion portion as a current collector lug part; and when the current collector lug part is placed upside, the expansion direction is the width direction of the electrode plate.
According to the present invention, a manufacturing method of a lead-acid battery electrode plate comprises the steps of: consecutively supplying a lead or lead alloy sheet; leaving a part in the vicinity of the center of the sheet as a non-expansion portion and expanding both sides like mesh to form a grid body, so that the non-expansion portion forms a current collector part of the electrode plate along an expansion portion in an up and down direction of the electrode plate; making one or more openings in a part of the non-expansion portion; filling active material paste into the grid body; and cutting the grid body to predetermined dimensions; wherein a part of the non-expansion portion is projected above the position of an upper margin of the cut expansion portion as a current collector lug part; and when the current collector lug part is placed upside, the expansion direction is the width direction of the electrode plate.
According to the invention, the electrode plate using the expanded grid body excellent in discharge performance and productivity can be provided particularly as a large-sized lead-acid battery electrode plate.